mnesia: Read schema user properties directly

Doing a proper transaction handling of user properties (in current
implmenentation) caused schema_transactions to be quadratic which
caused huge startup times for nodes with many tables since the merge schema
is a schema_transaction.

Do a direct read instead, cheap but implies that the plugin changes
will not be visible until the changes are commited and cannot be used
later in same transaction, which was possible before if undocumented
functions where used.

1 files changed, 3 insertions, 13 deletions

diff --git a/lib/mnesia/src/mnesia_schema.erl b/lib/mnesia/src/mnesia_schema.erl
index 0e4017e4c3..bb5e38f7c1 100644
--- a/lib/mnesia/src/mnesia_schema.erl
+++ b/lib/mnesia/src/mnesia_schema.erl
@@ -952,19 +952,9 @@ get_index_plugins() ->
     get_schema_user_property(mnesia_index_plugins).
 
 get_schema_user_property(Key) ->
-    Tab = schema,
-    %% Must work reliably both within transactions and outside of transactions
-    Res = case get(mnesia_activity_state) of
-	      undefined ->
-		  dirty_read_table_property(Tab, Key);
-	      _ ->
-		  do_read_table_property(Tab, Key)
-	  end,
-    case Res of
-	undefined ->
-	    [];
-	{_, Types} ->
-	    Types
+    case dirty_read_table_property(schema, Key) of
+	undefined ->  [];
+	{_, Types} -> Types
     end.
 
 get_ext_types_disc() ->